CV Business Times: UC Davis notes the obvious: Water can’t be stored if it’s not there in the first place

The Californians who bothered to vote this month bought into the tidal wave of promotion in favor of the water bond, passing the $7.5 billion plan by a wide margin – with 67.2 percent in favor.

Much of the money is supposed to be spent on building two new reservoirs, one in the Sierra Nevada on the upper San Joaquin River, and the other north of Sacramento to fill with water from the Sacramento River.

But the drought-prone state can effectively use no more than a 15 percent increase in surface water storage capacity because of lack of water to fill it, according to a new analysis released Thursday by the University of California, Davis.

The report by water engineers and scientists with the University of California, Davis, the Nature Conservancy and three prominent water consultants, says California could potentially use up to 6 million acre-feet in combined additional surface and groundwater storage — about a third more capacity than Shasta Reservoir, the state’s largest reservoir. Exceeding this expansion runs into limits of available precipitation and the ability to transport water, the report says.

“Reservoir storage does not equate to water supply,” said Jay Lund, lead author of the report and director of the UC Davis Center for Watershed Sciences. “Reservoirs cannot supply water without a water supply to fill them first.”

The report, “Integrating Storage in California’s Changing Water System,” evaluates the possibilities of increasing water storage capacity in the semi-arid state. The study does not encompass economic or environmental analysis to determine whether additional storage is justified. Rather, the researchers determined the maximum that could be used, both with and without coordination with other parts of California’s water system.

The study comes as the California Water Commission begins developing rules for allocating investments in storage projects from funds recently approved by California voters as Proposition 1. More than a third of the $7.5 billion is allocated for additional surface and groundwater storage. The bond does not specify individual projects, and the study does not consider any specific project proposals.

Overall, the report advocates a more integrated approach to surface and groundwater water storage where new storage projects are planned, designed and operated as components of a statewide water system.

Such an integrated, multi-benefit analysis would include a wide variety of water sources and delivery alternatives, and potential changes in how water is managed to meet California’s multiple water demands — flood management, energy production, water quality, recreation, and flows for fisheries and wildlife, the report says.

Such an approach would be a departure from most project analyses and policy discussions that examine water storage proposals as isolated projects, says co-author Maurice Hall, California water science and engineering lead for The Nature Conservancy.

“Our current water supplies are over-allocated, and we need to invest in a much smarter strategy to upgrade our water system and meet multiple water needs with an eye to the future and changing climate conditions,” says Ms. Hall. “We need to design the system for nature’s needs up front if we want to have healthy streams and rivers in the future.”

The authors say that with a science-based approach to investing in water storage projects, there is great potential to develop more sustainable storage and water management strategies. The report says integrated water projects are likely to “significantly outperform” individual projects in achieving multiple water management objectives.

The authors note that this study looks exclusively at storage considerations for surface and groundwater storage, and does not look at comprehensive water conservation strategies, system reoperation, water rights apportionment or other water policy considerations that may stretch existing water supplies.